Avoid Time-of-day Format Displaying elapsed time in the format of time-of-day (HH:MM:SS.SSS) is misleading and ambiguous as it can easily be misinterpreted as time-of-day. ISO 8601 – Duration Format The ISO 8601 standard defines sensible string representations of various date-time values. These values include elapsed time. The standard format is PnYnMnDTnHnMnS...

It sounds as if you are best saving the time in the controls as well as the time as a string. The Tag property is there for that purpose. See https://msdn.microsoft.com/en-us/library/system.windows.forms.control.tag%28v=vs.110%29.aspx So, for example, if you set the DateTime you are using into label2.Tag to the same time as you...